This invention relates to a block-graft copolymer useful as a material for various functional membranes including an oxygen enrichment membrane, and a process for producing the same.
At present, many attempts have been made on the development of functional polymer materials used for various purposes.
Dimethylpolysiloxane is known as a material for high enrichment of oxygen, but, when used in the form of a thin membrane, it can not stand use because of its weak cohesion. For this reason, it is attempted in the present state of the art to form the material as a block copolymer to remedy its disadvantage. However, although the block copolymer is useful for increasing mechanical strength, only the compositional proportion held by dimethyl polysiloxane affects oxygen enrichment and permeability, raising a problem that the oxygen enrichment performance decreases in proportion thereto. Dimethylpolysiloxane and high molecular compounds having an amino group or carboxyl group have biocompatibility, and some of them are used as biomedical materials such an antithrombrogenic materials, bioseparator materials and cell culturing materials. In particular, recently noted are high molecular materials, particularly block copolymers, containing the above macromolecule as a component, which is a multi-phase polymer with a clear micro domain structure. However, in order to obtain the block copolymer finely divided into multiphases, no other way is available than producing it according to a living anionic polymerization method, and also the manner of combination of monomers is restricted. Moreover, since the domain size of the microphase-separated gyration is governed by the radius of inertia, there is a problem that the domain size in the block copolymer can be controlled only with difficulty.